slide deck 4, exam 2

mortality and morbidity

what are mortality rates/ratios/proportions used to measure

measure and evaluate severity of clinical and public health indicators

there are so many ratios, rates and proportions available

why is mortality r/r/p a good measure

trends can be tracked over time and the data is reliable since everything is recorded

data needed to calculate mortality r/r/p

in the numerator is vital events and stats

in the denominator is the US census

what are vital events in the mortality numerator

the deaths that are certified and recorded in certain ways

there is a set of determinants by international classification of diseases (ICD)

how many standards in the ICD

10-11 standards now at this point

what is the US census in the denominator of mortality r/r/p

a tally conducted every 10 years for the house of representatives apportionment

435 members of house and 2 senators per state

how to find the actual cause of death on a death certificate

look above all “due to” lines

there is a sequence of events since the first and primary cause of death may be too niche

real trends in mortality

increases and decreases in mortality can be due to changes in survivorship with no new cases, changes in number of new cases that result in death and changes in age profile

false trends in mortality

increases or decreases in mortality can be due to death certification issues and census issues

what are some examples of death certificate issues

incorrect cause of death, error in age or sex, changes in IDC over time

explain how changes in ICD have impacts on the trends

a new added category results in a large jump

a disease that wasn’t for example called Alzheimers at first will result in a large jump

what are example of US census issues

counting errors and demographic classification errors

could be an undercount of people since some people do not fill it out

what is morbidity

illness/injury/sickness

what are morbidity rates and proportions used for

to measure and evaluate severity of clinical and public health problems using incidence and prevalence

morbidity versus mortality

morbidity is less reliable than mortality data since no formal record is kept and lots of illnesses go unreported

what is needed when calculating for morbidity r/r/p

medical records, interview, surveys, surveillance and US census

surveillance programs of morbidity

active and passive surveillance

what is active surveillance of morbidity r/r/p

case finding, seeking out and identifying cases of illness directly

more accurate

what is passive surveillance of morbidity r/r/p

mandatory reporting of notifiable diseases which relies on healthcare systems to report

what is incidence rate

measure of NEW CASES of a disease that occur during a specified period of time in a population at risk of developing a disease

what does incidence rate give you

it provides an estimate of the RISK presented by that disease within the population

this is most important with infectious diseases that spread

example in class of incidence rate data

the figure of HIV surveillance that shows that ages 20-23 are at highest risk of HIV ages 13-19 are at lowest risk of HIV

when is a case considered to be a new case (for incidence)

at the time of a disease onset also known as when the disease starts

how to consider an acute disease a new case? (for incidence)

usually is obvious

the example is with a heart attack the onset time is obvious of the heart attack (also can be infectious disease or injury)

how to consider a long incubation or induction period as a new case (for incidence)

this is now more unclear, mostly non infectious, chronic diseases and psychiatric disorders

what is the date of diagnosis often used as (for incidence)

the date of onset for all types of diseases

this is done since it may be impossible to identify the time of disease onset

how is the population at risk defined (incidence)

if you already have it, you will not be at risk

most worth the counting and guessing within common disease (not worth it with rare disease)

Usually the entire population is considered to be a risk

comparison between leaving out unsusceptible population with incidence (uterine cancer)

a larger value in the denominator (all women) will have a small value of incidence

a small subset in the denominator (women who got a hysterectomy) will have a large value of incidence

in incidence, what can be done to substitute for the denominator (people at risk)

person time denominator

what is person time denominator (incidence)

a replacement or substitute for total population at risk when small populations are under study or when the time is longer than one year

each person and how long they were in the study

example of person time denominator from textbook

total number of subjects was 50 divided by total person-time which was 461 = 1.08

if the population did not change from say october 2017 to february 2018, what can you do with incidence rate

an estimate incidence rate can be done because the population at risk remains constant over a period of time

what are attack rates (proportion since its a percentage) of incidence

a measure of risk of disease for a small group of people exposed to some factor when incubation period is short

example is the train chemical spill in eastern ohio or an outbreak on a cruise ship

what is a prevalence rate/proportion

measure of total cases of a disease present at a particular time

there is point and period

incidence versus prevalence

incidence used for new cases and prevalence used for all total cases

what specifically does prevalence measure

all cases of a given disease (new and old)

it measures the burden of that disease in a population, not the risk

when is prevalence useful

for planning in public health and for medical services/infrastructure

example of prevalence graph in class (COPD)

there is more prevalence of COPD in kentucky, west virgina and tennessee since there used to be lots of mining and many many smokers

in utah there us low prevalence since there is a young population that does not smoke

incidence versus prevalence data in class example (HIV)

the prevalence line is way higher than the incidence line since HIV has medications, suppressives and therapy which accounts for higher prevalence

there is a higher number of total cases of HIV since many people are surviving it, living and being treated and not a lot of new cases (incidence)

there are less new cases of HIV since we have vaccines

what is point prevalence

most commonly used when you think of prevalence

its the measure of total cases at a particular time (a snapshot)

what is period prevalence

measures the prevalence of who was sick at the beginning of time period plus any new cases that develop during that time period

what happens if prevalence is constant

the new cases and the cure/deaths are the same

what happens if prevalence is decreasing (can be good or bad)

the number of new cases decreases (new prevention)

the number of cures (new drugs) and deaths (drug resistance and more lethal) both increase

what happens if prevalence is increasing

the number of new cases (more people developing, new tests that identify the disease earlier) increases

the number of cures (no cure from failure of drug but patient still lives) and deaths (new drugs developed that prolongs life but no cure) both decrease